One of the most pressing challenges in the design of soft nanomaterials is the fabrication of selective molecular size nanopores in nanothin membranes. Selective nanopores can be extremely useful in such applications as DNA sequencing, fabrication of nanobioreactors, nanoelectronics, and advanced drug delivery devices. (Bayley, H.; Martin, C. R. Resistive-Pulse Sensing—From Microbes to Molecules. Chem. Rev. 2000, 100, 2575-2594; Kasianowicz, J. J.; Brandin, E.; Branton, D.; Deamer, D. W. Proc. Natl. Acad. Sci. U.S.A. 1996, 93, 13770-13773; Alper, J. Science 1999, 284, 1754-1754; Vriezema, D. M.; Aragones, M. C.; Elemans, J. A. A. W.; Cornelissen, J. J. L. M.; Rowan, A. E.; Nolte, R. J. M. Self-Assembled Nanoreactors Chem. Rev. 2005, 105, 1445-1489; Nardin, C.; Thoeni, S.; Widmer, J.; Winterhalter, M.; Meier, W. Chem. Commun. 2000, 1433; Lin, Z., Kim, D. H., Wu, X., Boosanda, L., Stone, D., LaRose, L. & Russell, T. P. A rapid route to arrays of nanostructures in thin films. Advanced Materials 2002, 14, 1373-1376; Jeong, U., Ryu, D. Y., Kim, J. K., Kim, D. H., Wu, X. & Russell, T. P. Precise control of nanopore size in thin film using mixtures of asymmetric block copolymer and homopolymer. Macromolecules 2003, 36, 10126-10129; Wei, Y.; Qiu, K.-Y. Ser. Chem. Eng. 2004, 4, 873-892; Desai, T. A.; Hansford, D. J.; Kulinsky, L.; Nashat, A. H.; Rasi, G.; Tu, J.; Wang, Y.; Zhang, M.; Ferrari, M. Nanopore technology for biomedical applications Biomed. Microdevices 1999, 2, 11-40; each of which is hereby incorporated by reference in its entirety.) Currently existing nanothin films having selective pores do not have the advantages of the present invention. The present invention discloses a method for the fabrication of nanothin materials with controlled size nanopores and demonstrates size selective permeability with the size probe retention assay.